Example of receiving an mqtt temperature for https://github.com/KhaosT/HAP-NodeJS

Outside_accesory.js

var OutsideTemperature = 0.0;

// MQTT Setup
var mqtt = require('mqtt');
console.log("Connecting to MQTT broker...");
var mqtt = require('mqtt');
var options = {
  port: 1883,
  host: '192.168.4.24',
  clientId: 'AdyPi_OutsideTemperatureSensor'
};
var client = mqtt.connect(options);
console.log("Outside Temperature Sensor Connected to MQTT broker");
client.subscribe('/house/weather/outside1/temperature/current/1');
client.on('message', function(topic, message) {
  console.log(topic + ' -> ' + parseFloat(message));
  OutsideTemperature = parseFloat(message);
});

var Accessory = require('../').Accessory;
var Service = require('../').Service;
var Characteristic = require('../').Characteristic;
var uuid = require('../').uuid;



// Generate a consistent UUID for our Temperature Sensor Accessory that will remain the same
// even when restarting our server. We use the `uuid.generate` helper function to create
// a deterministic UUID based on an arbitrary "namespace" and the string "temperature-sensor".
var sensorUUID = uuid.generate('hap-nodejs:accessories:temperature-sensor');

// This is the Accessory that we'll return to HAP-NodeJS that represents our fake lock.
var sensor = exports.accessory = new Accessory('Outside Temperature Sensor', sensorUUID);

// Add properties for publishing (in case we're using Core.js and not BridgedCore.js)
sensor.username = "C3:5D:3A:AE:5E:FB"; // needs to be unique if you have multiple accessories
sensor.pincode = "031-45-154";

// Add the actual TemperatureSensor Service.
// We can see the complete list of Services and Characteristics in `lib/gen/HomeKitTypes.js`
sensor
  .addService(Service.TemperatureSensor)
  .getCharacteristic(Characteristic.CurrentTemperature)
  .on('get', function(callback) {
    
    // return our current value
    callback(null, OutsideTemperature);
  });

// randomize our temperature reading every 3 seconds
setInterval(function() {
  
  // update the characteristic value so interested iOS devices can get notified
  sensor
    .getService(Service.TemperatureSensor)
    .setCharacteristic(Characteristic.CurrentTemperature, OutsideTemperature);
  
}, 3000);